We propose to continue studies on H ion and K ion transport by gastric vesicles. We shall relate these transport reactions to the kinetics of the ATPase and the reactions of the phosphorylated intermediate. Tissue localization of the ATPase will be continued using antibodies and membrane orientation by labelling techniques. BIBLIOGRAPHIC REFERENCES: Saccomani, G., Schackmann, R., Rabon, E., Hung, H., Sachs, G.: Transport properties of hog fundic membranes. Biophysical Society Meeting, 16, 128a, 1976, Biophysical Journal Number 21, part 2. Sachs, G., Hung, H., Rabon, E., Schackmann, R., Saccomani, G.: Transport by K ion ATPase of gastric mucosa. Gastroenterology 70: #5, part 2, p. 932, 1976.